2022-04-08

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Introduction

The woodland caribou Rangifer tarandus caribou in Canada’s boreal forest ecosystems are threatened. The Species At Risk Act lists R. tarandus caribou as threatened, and the Alberta Wildlife Act lists the species as threatened.

Hereafter boreal caribou (or just caribou) will refer to Rangifer tarandus caribou in Alberta, unless noted differently.

The national Species At Risk Act defines a threatened species as those which

“are likely to become endangered if nothing is done to reverse the factors leading to their extirpation or extinction”

(Environment Canada, A Guide to the Species At Risk Act (SARA)).

Caribou habitat requirements

Caribou are adapted to a boreal environment in which the main disturbance to habitat is wildfires, but human development and use of land in the boreal zone degrades the habitat and reduces the amount of habitat available to caribou (Environment Canada, Woodland Caribou, Boreal population).

For boreal caribou to succeed, the habitat available to them must be, or is:
  • Large and uninterrupted woodland or forest, wetland, bog, or fen, with
  • Sufficient tree and ground lichens for winter foraging, and
  • tall, thick grasses, sedges, forbs, horsetails, and shrub leaves for summer foraging.

(Environment Canada, Woodland Caribou, Boreal population)

Caribou habitat selection

“Boreal caribou tend to avoid cleared areas where shrubs favoured by moose and deer are more abundant”

(Environment Canada, Woodland Caribou, Boreal population).

Caribou are cryptic animals, and their extra-species avoidant behaviour means they do not tolerate noise, light, or the presence of other animals well.

Particular to their requirement of large, undisturbed habitat is the edge-effects the habitat can experience. If a habitat would otherwise be suitable to caribou, they may not utilize it because of small interruptions of developments. In a 6000 sq. km area, Dyer et al. found that just one percent (1%) use of the area by humans reduced the use of the same area by boreal caribou to fifty-two percent [52%; -Simon J . Dyer , Jack P . O ’ Neill , Shawn M . Wasel].

The Albertas government’s DRAFT Provincial Woodland Caribou Range Plan defines disturbed habitat as

“Habitat showing:

  1. human-caused disturbance visible on Landsat at a scale of 1:50,000, including habitat within a 500-metre buffer of the human-caused disturbance;

  2. and/or, fire disturbance in the last 40 years, as identified in data from each provincial jurisdiction (without buffer)”

(Government of Alberta)

However, the total impact on caribou habitat may be larger, as the scale of land-sat imagery used to detect and calculate habitat disturbance is large. A \(1:50000\) scale means that \(1cm\) of the satellite image corresponds to \(50000cm\), or \(0.5km\)! For most linear features like seismic lines, they do not appear on imagery such as this. The conservation efforts surrounding boreal caribou are not naive, however, and the linear features have been mapped at higher resolution scales and have been accounted for.

The general conclusion is small amounts of human usage of critical boreal caribou habitat result in significant reductions of habitat land usage.

Alberta’s Boreal forests

Alberta’s boreal forests extend from the northern Rocky Mountains and northern foothills through the rest of northern Alberta.

Despite the large size of the boreal-zone in Alberta, the boreal forest ecosystems are severely degraded due to linear features (entities that occur in relatively straight lines), particularly by roads, rail-ways, and specially seismic lines.

Seismic lines are straight (or linear) clearings of trees that are used during oil and gas exploration, and historically they had an approximate width of up to ten meters (\(10m\)), but modern, lower-impact seismic lines (LIS) can have widths as small as one and a half meters (\(1.5m\)).

The extent of linear features in Alberta’s boreal forests is significant, with aprpoximately \(250000km\) of conventional seismic lines present, and sixty percent (\(60%\)) of these conventional (historical) seismic lines would require significant restoration effort, such as tree planting (Hill et al.; Government of Alberta).

Alberta’s caribou ranges, undisturbed habitat

Unfortunately, in the five years prior to the publication of the government of Alberta’s draft range-plan for boreal caribou conservation, all but two populations experienced decline in the percentage of undisturbed habitat available to them. The three largest decreases were in the caribou ranges of Slave Lake (\(-29.7%\)), followed by Nipsis (\(-26.5%\)), and Little Smokey (\(-20.0%\)).

Particularly worrying, is that as of the publication of Hill et al. the Little Smokey caribou range has only \(4%\) undisturbed habitat. The Little Smokey population of caribou is likely to remain designated as threatened and not self-sustaining for many decades.

The twelve populations in Alberta in the figure below are faceted (each sub-plot) by the quartile the size of their range (in hectares). The data for both the chart and table is from Hill et al.

The percent change in the area of undisturbed boreal caribou habitat, by population, from 2012 to 2017. Negative numbers indicate that the area of undisturbed habitat has descreased from 2012 by the percentage given. Positive values indicate an increase in the undisturbed habitat, reflecting either a change in data collection or restoration of previously disturbed habitat.
Population (range) Percent change (in undisturbed habitat) from 2012 to 2017
Slave Lake -29.730
Nipsis -26.471
Little Smokey -20.000
Yates 1.266
Cold Lake -14.286
Richardson -1.282
East Side Athabasca River -4.348
Bistcho 7.692
West Side Athabasca River -6.250
Caribou Mountains -5.195
Red Earth -7.143
Chinchaga -19.231

This map from the Government of Alberta shows the ranges of boreal caribou, and other features of Alberata, and helps to visually understand the size of these ranges. The Little Smokey and Slave Lake ranges in particular are quite small for caribou, despite their large geographic size for what a human considers a large area.

Seismic lines in Alberta

The following two figures are from Dabros et al. The first is Fig. 1 of that publication, and the second is Fig 2. of that publication.

Panel \(C\) of figure 2 shows a lower-impact seismic line, and the impact on the shrubbery this method still causes. Moreover, the practice of LIS includes creating the lines in winter, which does reduce the amount of damage to the forest understory, but during winter this scare away any boreal caribou in the nearby area that hear the destruction, and they may not return for many weeks.

References

Alberta Environment and Parks. Alberta Caribou Ranges Map. 2017.

Canada, Environment, and Climate Change. Amended Recovery Strategy for the Woodland Caribou (Rangifer tarandus caribou), Boreal Population, in Canada 2020. Environment; Climate Change Canada, 2020, https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/recovery-strategies/woodland-caribou-boreal-2020.html.

Dabros, Anna, et al. Seismic lines in the boreal and arctic ecosystems of North America: Environmental impacts, challenges, and opportunities.” Environmental Reviews, vol. 26, no. 2, 2018, pp. 214–29, https://doi.org/10.1139/er-2017-0080.

Environment Canada. A Guide to the Species At Risk Act (SARA). 2007, pp. 1–4, https://www.registrelep-sararegistry.gc.ca/6AC53F6B-550E-473D-9BDB-1CCBF661F521/fedland-eng.pdf.

—. Woodland Caribou, Boreal population. 2012, https://www.nrcan.gc.ca/our-natural-resources/forests/sustainable-forest-management/conservation-and-protection-canadas-forests/woodland-caribou-boreal-population/13201.

Government of Alberta. Provincial Woodland Caribou Range Plan: Alberta’s Approach to Achieve Caribou Recovery (Draft). Government of Alberta, 2017, p. 212.

Hill, Dorothy, et al. Status of Boreal Woodland Caribou Conservation in Canada: A summary of range planning, restoration, and opportunities to win on caribou and climate. no. November 2021, 2021, p. 98, pembina.org.

Simon J . Dyer , Jack P . O ’ Neill , Shawn M . Wasel, Stan Boutin. Avoidance of Industrial Development by Woodland Caribou Author ( s ): Simon J . Dyer , Jack P . O ’ Neill , Shawn M . Wasel , Stan Boutin Published by : Allen Press Stable URL : http://www.jstor.org/stable/3803106 Your use of the JSTOR archive indicates y.” The Journal of Wildlife Management, vol. 65, no. 3, 2001, pp. 531–42.

Smith, S. Trends in permafrost conditions and ecology in northern Canada.” Canadian Biodiversity: Ecosystem Status and Trends 2010. Technical Thematic Report No. 9. Canadian Councils of Resource Ministers., no. 9, 2011, p. 27.